Ferritic aluminum-iron base alloys and method of producing same



FERRITIC ALUMINUM METHOD OF PRODUCING SAlVIE Nachman and William J.Buehler, Silver Spring,

of one-fourth to EdwardrA. Gaugler,

No Drawing. Application August 6, 1954 Serial No. 448,398

, 27 Claims. (Cl. 1482) (Granted under Tifle, 35, U. S. Code (1952),see. Zoo) The invention described herein maybe manufactured and used byor for the Government of the United States of America for governmentalpurposes without the payment of any royalties thereon or therefor.

The present invention relates to a series of alloys for high temperatureand magnetic uses, and more particularly to the method and processingtechnique essential to produce physically sound high quality materials.

Heretofore, certain known alloys of aluminum and iron possessedexcellent oxidation resistance when heated to a high temperature in air.However, such alloys were weak in structure and lacked high temperaturestrength, and desired malleable characteristics such that they could beformed into any desired shape. To take advantage of the high temperatureoxidation and hightemperature strength possibilities the aluminumcontent of these alloys must be rather high [minimum of about Al].Considerable difficulty, however, was encountered in-melting,- casting,rolling, and processing, even binary AlFe alloys, into cold rolled sheetform when the aluminum content exceeded 10%. Moreover, due to theinherent brittle characteristics of the binary Al-'-Fe alloys with theAl content exceeding 10% no successful method has been devisedheretofore to produce a usable and workable sheet material from suchalloys, having strengthening additives such, for example, as Mo, V, Ti,Ta, Cb, Cr, W, and B. Nor was it possible heretofore to hot and coldroll such materials containto Stephen Girard Lax,

' United Statcs-Patent'O -IRON BASE ALLOYS AND r and improved method ofalloys into workable sheet high tensile strength and high resistance tocorrosion Patented Nov. 4, 1958 cial ferritic type high temperaturematerials currently:

being used in high temperature applications.

devised for rolling such component inexcess of 10% into physically soundusablematerial'" and processing the alloys'into various forms, thin coldrolled sheets.

An object of the present invention is to provide compositions offerritic alloys having excellent high temperature strength andoxidationresistance. P

including Another object of the invention is to provide a new? andimproved method of making aluminum-iron base alloys into usable materialhaving improved high temperature and magnetic properties. 7

Another object of the invention is to provide a new processingaluminum-iron base and oxidation.

Another object of the e, of aluminum-iron base materials capable ofbeing exing three or more of the aforesaid metals into physically soundflexible sheets of any desired and workable thickness. I

The present invention contemplates the provision of a new series offerritic high temperature and magnetic alloys containing non-strategicmaterials, such, for exmaterial characterized by invention is to providea series "truded by standard hot extrusion methodsinto usable shapespossessing the magnetic and high temperature properties associated withthese alloys.

Still another object of the invention is to provide a series ofmaterials with a very high electrical'resistivity' microohm-Cm] coupledwith the excellent'high temperature properties suitable for use inelectrical resistance heating applications.

A further object of the invention is for producing a series of materialsexhibiting good. re-' sistance to wet corrosion, at room temperature,when. 'I

brought'in contact with common corrosive mediums;

A still further object of the invention is to provide a method forproducing a series of magnetic materials high hardness and wearresistance.

A still further. object of the invention is to a series of alloys'inusable form such, for example, as sheets, castings and the like,

at room temperature and at elevated temperatures.

Other objects and many of the attendant advantages of this inventionwill be readily appreciated as the same becomes better understood byreference to'the' following detailed description. A 1

In accordance with the present invention the alloy compositions mayconsist of 10 to 18% Al, 0 to 5% of to provide a method possessingexcellent magnetic properties coupled with 'a provide exhibiting secondphase precipitation phenomena to strengthen the materials both any oneorany combination of the following elements- Mo, V, Cr, Ti, Ta, Cb, W,and B, the remainder or basic alloy being Fe.

Using the methods of. limits in accordance with the present inventionthe lowing stress-rupture results were actually achieved, the 7 resultsbeing set forth on the following chart 'Ol'ialfl with the alloycompositions given andv the respective. heat treatments and materialform included.

fabrication and composition fol- High temperature stress-rupture dataStress-Rupture Times in Hrs. Sample N 0. Alloy Composition Form of AlloyHeat Treatment Using 25,000

Material p. s. 1. load and tested at 1,200 F.

15.6% A1, Remainder Fe 0.020 thick cold None 0.5

rolled sheet. 15% A1, 3.3% Mo, Remaindo 1,050 O.fr2hrs.iol1owed 47. 6

der Fe. by an air cool. 175%?1, 3.3% Mo, Remaindo o 69 er e. 17.2% A1,3.3% Mo, Redo 900 C. for 2 hrs. followed 24 in der Fe. by an air cool.A1, 3.3% Mo, Remain- --do 1,050 C.ior2hrs.iollowed 0.25

der Fe. by an air cool. 13.8% Al, 4% Mo, Remaind0 d0 54.4

der Fe. r 16% a1, 3.3% M0, 0.05% 0, -do d0 19.3 14 r rii 2f i' it iiav vV d 7 a 17 2 x .1, y "1 ,0 O 155,311,573 Mo, R'einamder ..-do do e1 '6.w I mg ai, 1.68% M0, 0.3% Ti, ..-do do 73. 2 e. a 167311, 1% Ti, .Bal.Fer; do do 9. 9

From the foregoing table of stressqupture data the following conclusionsare obvious:

(I) The basic binary alloy containing about 16% Al, the remainder iron,-in the cold rolled sheet form, with no heat treatment has a very 'lowhigh temperature strength.

'(2) The addition of elements such as M0, V, and Ti definitely improvethe-high temperature strength.

(3) Coupled with the aforesaid additives, 'maximum high temperaturestrengths are attained by -a heat treatment of about I050 C. for about 2hours followed by a still air cool. The effectiveness 'of this'heattreatment can be seen try-comparin samples 3 and 4 in the table.

(4) The percentage of aluminum 'and 'iron present 'in the alloy as showninth table, in combination with the other elements greatly improves thehigh temperature strength. This can be shown by comparing samples 2 and5 in the table.

(5) Higher percentages of elements, siic-h'a's -Mo, increase the hightemperature strength. However, the'reis a "practical limit on coldrolled areencountered.

(6) The addition of the etements such'as-Mo, V, and Ti -is for thepurpose of increasing the -high temperature strength of the basic Al ingthe existingferritic solid 'solutiono'r by precipitating a.strengthening second phase. These element additions appear to have verylittle'efle'ct upon the grain size or oxidation resistance of'theresultant alloys.

These sample data given in the table further illustrate the nature ofthis inventiomhowever, it should be understood that the-invention is notres'trictedto these specific examples.

The high temperatureand rhagnetic alloy ofthe inst'aht 4 sheetmaterialthat limit being the composition where difliculties in coldroning} e alloys by either strengthe'n- Y invention may be made, *forexample, by-melting togethera an alloy of 10 to 18% aluminum, up to '5strengthening element additives, the remainder of the alloy being iron,forminga casting or shape, solution heat treating the casting to atemperature within the single phase solid solution region, 'When thishas been done the shape or casting is rapidly cooled to a temperaturewithin the multi-phase region, andthe'castin'gor shape-is maintained atthis reduced temperature until at least one other phase hasbeenprecipitated. ,7 The term strengthening element? as einployed hereinand in the appended claims is' defined as an element such, for example,as M0, V, Ti, Cr, Ta,

ande, or any combination thereof.

Cb, W, Ni,

W .heat treatment eonsists of=heating the alloy to a'tem'pera-. V

'ture of about -0 -C. 'for Magnetic data Nominal alloy composition 6%A1, 3.3% Mo, re

mainder -Fe. 1050 C. for one hour,

Heat treatment furnace cool to 600 oersteds.

Based '-'-1ipon actual tests and data '-'obtain'eii on these uniquealloys fabricated in accordance-with the teaching of the presentinvention, there areeeitainfcoinbinations and qiiantities of metallicelements th'zit'rnu's't-be alloyed to produce high temperature materialswith suitable strength and oxidation resistance.

be 'from "about-l0 to 18% Added to the Al'i's 'a'nother'type-el'ement orelementsfsuch in the alloyeither as a siiigle' element added to the Aland Fe, tor in combinations of two, or more of these elements.

the alloys however, are composed of basically iron and aluminum withoneor more of the elements Mo, V, Ti, Ta, Cb,-Cr, W, and B present.

In addition to-the optimum alloy compositions, and

alloy fabrication IhBthOdSftO'Obtfiill the maximum hightemperaturestress-rupture.strength in these materials it is essential to:perform certain heat treating operations upon thefabricated-material ashereinbefore set forth "in greater detail. By actual tests, the mostsatisfactory about two hours followed by a still-air cool.This=heat-treatment cyclewas'applied to 0.020 thick Sheet material,however, ifthicker'secr [at ;H =-30. -oerstedsl The's'e quantities maybe summarized iris-follows: Thehliiniinuih 'eon'tent s'liould 'of totalalloy by weight;

' The amountfofany one or more but not all of the elements Mc, V, Ti,Ta, Cb, 'Cr, W, and B, present amo tions or sheets are heat treated,longer times of holding at 1050 C. and more rapid cooling means may beneeded to elfect the same heat treating cycle.

Moreover, when a fine grained sheet material is desired the cold rolledsheet alloys may be recrystallized at about 750 C. for 1 hour. By actualtests it has been found that this recrystallized fine grain size is onlypossi-- ble from cold worked sheet alloys.

Material fabrication method Melting and casting The melting of theaforesaid alloys may be performed in any suitable type of meltingfurnace, such for example, asa vacuum or controlled atmosphere inductionfurnace. For the purpose of clarity in describing the operations, anexample melt of 16% All, 3.3% Mo, 80.7% Fe will be described. The is tomelt the iron and molybdenum under vacuum. The melting is preferablycarried out in a magnesium oxide crucible. After the elements arecompletely melted, wet and dry hydrogen gas is passed over the melt.This operation is performed for the purpose of decarburizing anddeoxidizing the iron-molybdenum molten solution. Helium is nowintroduced into the tank to displace the hydrogen. When the gaseousmixture in the furnace chamber no longer supports a combustion, it willbe understood that such action removes most all of the hydrogen that mayhave been dissolved in the molten alloy. Helium is introduced again intothe furnace chamber until one atmosphere of helium is present. At thistime the 16% of aluminum is added to the melt and the furnace chamber isagain evacuated [using a vacuum pump] to a pressure of 5 millimeters ofhelium. When this pressure is attained, and the optimum pouringtemperature reached, the melt into a suitable mold for shaping thematerial into a final cast shape or it may be poured into aningot orslabtype mold, forming an ingot or slab for subsequent roll ing, swagingor extrusion into strips, sheets, rods, wire or other shapes.

The operation of pumping down to 5 millimeters of helium pressure afterthe aluminum addition and prior to Pouring is an important and essentialstep in the process. First, it removes the hydrogen from the moltenalloy, thus producing sound castings. Secondly, coupled with the molddesign it promotes a more desirable solidification rate for the moltenalloy thus producing a highly desirable fine and equiaxed cast grainsize. If thesame melt is poured at one atmosphere of helium, using thesame mold, a large grained columnar cast structure would result. Whenthe same melt is poured at one atmosphere of helium into a ceramic moldan equiaxed structure results and a much larger grain size is evident.Thus by the aforesaid treatments it is apparent that it is possible toproduce the type of cast grain formation and size of cast grain byvarying the rate of solidification of the alloy.

By actual test it has been found that casting such alloys in a steelslab mold under a vacuum of 5 mm. of helium and containing 16% A1, 3.3%Mo, and 80.7% Fe produced a desirable fine equiaxed cast grainstructure, the casting in a steel slab mold under one atmosphere ofhelium produced a less desirable large columnar cast grain structure andthe casting in a ceramic mold under one atmosphere of helium produced alarge and equiaxed cast grain structure.

It will be understood that the formation ot a fine equifirst step in themelting operation is poured. Pouring may be either axed castgrainstructure is an important step in the production'of good qualitymaterial. Large columnar cast.

grain structure causes hottearing 'or crackingduring fabrication. Hottearing or cracking is practically nonexistent in slabs with a fineequiaxed cast grain structure;

Conditioning cast slabs Immediately following the pouring, the cast slabhours and allowed to cool with the furnace, about 30 C.

drop'in temperature per hour. This operation prevents u the cast slabfrom cracking during rapid cooling'following solidification after theheat treatment, if desired, the" slab may be machined free of surfaceimperfections be fore beginning the hot rolling-operations. 'Machined tocrack severely during hot-working.

Hot rolling After melting, casting and conditioning the'slab, the hotrolling operation is in order. The slab is hot rolled to about 0.250" inthickness at a temperature of 1050" C. The reductions in thicknessbetween reheatings and v the reductions per pass through the mill arebased upon the-mill capacity and the rate at which the strip loses heat.Rolling is stopped and reheating is necessary when the strip drops intemperature to a dull red heat. At a thickness of about 0.250", the hotrolling is performed at about 950 ,C. When the strip has been finishedto about 0.125 or preferably 0.1", the cold rolling operation is inorder.

It has been found during the rolling operation that some of theaforesaid materials can be successfully hot.

rolled in the Sendzimir Hot Mill reducing a 1.0" slab to about 0.1"thick in one pass.

Conditioning'prior to cold rolling Any surface imperfections present onthe hot rolled strip may be removed prior to thebeginning of the coldrolling operation in the aforesaid manner. The removal of theimperfections will not effect the material. In 7 reality this operationimproves the surface of the material for the final cold rollingoperation.

Cold rolling This rolling operation is performed at about 575 C.,

and may be considered cold rolling for the reasons that the temperatureis below the recrystallization temperature.

It will be understood that cold rolling denotes cold working the alloyat a temperature below the recrystallitemperature.

rolling process, the crystal structure remains unrecrystallized and thecrystals are'elongated. Rolling at about 7 575 C. gives the material aregular cold worked appearance and elongates the grains intolong'fibered structure. The greater the percentage of cold work, thehigher the mechanical properties of the alloy .[tensile strength,

yield trength, hardness, impact strength, etc.]. Cold rolling may beperformed to reduce the material to -a relatively thin gage, such, forexample, as 0.002 of an inch or thinner.

Removal of oxide coating After rolling the material into strip form of asuitable thickness, it has a naturally formed coating of aluminum andiron oxides upon the surface.

should be stripped from the mold while'still red hot. The hotslab isthen placed in a furnace at 1050 C. for about two If it is desired .to.remove this coating for any purpose, lspotwelding';

Cold rolled strip "of a reasonable thickness may ,be formed' andshearejd if warmed. The. exact temperature of warming is dependent. uponthe forming configuration and material thickness of the alloy; V

The slabs or sheets. produced by the aforesaid method may be of anydesired length andwi'dth and characterized by high tensile strength :andhigh resistance to.

corrosion .and oxidation at elevated temperatures. This material is.suffi'cientl'y ductile to be readily"worked' or. shape without damage orformed into any desired breakage thereof. Furthermore, it has been foundby actual test that the metallic sheets produced in accordance with thepresent invention are about lighter than stainless steel alloys 'and thephysical and chemical characteristics thereof include high tensilestrength and high resistance to corrosion and oxidation. .Moreover,creep-rupture tests have proven that the aforesaid ma terial is farsuperior to some forms of the critical stainless steel alloys now being"widely used. It has been further found that because'of the highelectrical resistivity of the aforesaid material, the material isadmirably suited for use in heater elements, low temperature furnaces,and other numerous electrical appliances. It has also been found thatdue to the electrical resistivity and excellent magnetic characteristicsof these cold rolled almay be removedby the folsolution by loys, thesealloys are well. suited for magnetic applications.

From the foregoing, it will be apparent that 'new and improved ferriticmaterials and the method of making same has been invented, wherein suchmaterials are characterized by high tensile strength and high resistanceto corrosion and oxidation at elevated temperatures, high electricalresistivity, ductile to be readily formed into various forms includingthin tape-like strips or sheets and which is well adapted to extrusion.

Obviously many modifications and variations of the present invention arepossible in the light of the above teachings. .It is therefore to beunderstood that Within the scope'of the appended claims the inventionmay be practiced otherwise than as specifically described.

What is'elaimed as new anddesired to be secured by Letters Parent of theUnitedState's is:

l. The method of making a high temperature and magnetic alloy containingfrom 10 'to 18% aluminum, up to 5% 'o 'fa'strengthening element and theremainder iron, which consists 'of'meltingthe constituents in a suitablemelting apparatus to -form a molten alloy, forming the moltenalloyintoan ingot, controlling the solidification'rateof the molten 'alloy'toproduce an ingothaving a fine equiaxed cast grain structure,transferring the ingot from the 'melting apparatus while red hot to aheating apparatus andheat'treating the ingot at a*ternperature of about1050" C. for a time sufii'cient to uniformly heat the ingot, slowcooling theingot ata rate of about C. per hou r until theingot issubstantially at room temperature, removing surface imperfections fromthe 'ingot, hot Working the ingot into a sheet substantially .250 of aninch thick at a temperature-of about 1050 C. followed by hot working thesheet at a temperature and whichis sufiiciently tough and of 350 C. froma thickness of 0.250 of an inch thick to 'a (thickness of substantially0.125 of an inch, and thereafter cold working the sheet 'to 'a"predetermined thickness at a temperature of "575 C.

asuitable melting apparatus to jform a molten array, T

fomfring use molten :alloy into an. ingot, controlling thesdlidifica'tionrateof the molten alloy to produce anfin;

got having a fine equiaxed cast grain structure, trans fern'ng the ingotfrom :the melting apparatus while red hot to a heatingapparatus and.heattreating the ingot 1 at a temperature of about 1050 C. for a timesutficient; to uniformly heat'theingogjs'low cooling the ingot'ajt r tof. about 30, C. Per hour until .the ingot is sub'-.;stantiaIly-jatflrfoom(temperature, removing snrfacei impeifectio' nsfrom the ingot,- hot working the mgot mtoj."

a sheetfsubstantially "0.25.0" thick at a temperature; of about'l050 C.followed by hot working ,the'sheetlat; a,

temperature of 950 C. from a thickness of 0.250 of I an inch thick to athickness of substantially 0.125-of an inch,..and thereafter coldworking the sheet to..;the

desired thickness at a temperature of about 575. C. 3. The method ofmaking a high temperature and magnetic sheet alloy containingessentially 16% alurninum and up to 5% molybdenum and remainder iron,which consists of melting the constituents in a suitable. meltingapparatus to form a molten alloy, forming. the: molten alloy into aningot, controlling the solidifiea-Y tion rate of the molten alloy toproduce an ingot having a line equiaxed cast grain structure,transferring the in-. got from the melting apparatus while red .hot to a:heatn ing apparatus and heat treating the ingot at a temperatu're ofabout 1050 'C. 'for a time sufiicient to uniformly heat the ingot, slowcooling the ingot at a rate of about 30 C. per hour until the ingot issubstantially atroom temperature, removing surface imperfections from.the ingot, hot working the ingot into sheet substantially 0.250 thickat a temperature of ab0ut.l050 C. followed by hot working .the sheet ata temperature of 950 C.

from a thickness of 0.250 of an inch thick to a thickness.

of substantially 0.125 of an inch, and thereafter cold working the sheetto a desired thickness at a temperature of about 575 C. V 4. The methodof making a high temperature and."

magnetic sheet alloy containing essentially 16% alumi num, 3.3%molybdenum, and remainder iron, which consists of melting theconstituents in a suitable melting. apparatus to "form a molten alloy,forming the molten alloy into an ingot, controlling the solidificationrate' of the molten alloy to produce an ingot having aIfine' equiaxedcast grain structure, transferring the ingot from the melting apparatuswhile red hot to a heating apparatus and heat treating the ingot at atemperature,

of about 1050 C. for a time suflicient to uniformly heat the ingot, slowcooling the ingot at a rate of about 30 C. per hour until the ingot issubstantially at'room temperature, removing surface imperfections fromthe ingot, hot working the ingot into a sheet substantially, 0.250"thick at a temperature of about 1050 C. followed by hot working 'thesheet at a temperature of 950 C. from a thickness of 0.250 of an inchthick tea I thickness of substantially 0.125 of an inch, and thereaftercold working the sheet to a desired thickness at 1 a temperature ofabout 575 C.

5.1'I'he'method of making a high temperature and magnetic sheet alloycontaining essentially .l6% alumi-' num, essentially 2% Mo, essentially0.3% Ti, andthe remainder iron, which consists of melting theconstituents together to form a molten into an ingot, controlling thesolidification rate of the molten'alloy to produce aningot having a fineequiaxed 7 cast grain structure, uniformly heating the ingot while theingot is still red hot toa temperature of 1050 C., j slow cooling theingot at a rate of about "30 "C. per hour until the ingot issubstantially at room temperature, machine working'theingot free ofsurface imperfections,

alloy, forming the molten alloy I hot working the ingot above therecrystallization temessentially 2% Mo, essentially 0.3% Ti, and theremainder iron, which consists of melting the constituents in a suitablemelting apparatus to form a molten alloy, forming the molten alloy intoan ingot, controlling the solidification rate of the molten alloy toproduce an ingot having a fine equiaxed cast grain structure,transferring the ingot from the melting apparatus while red hot to aheating apparatus and treating the ingot at a temperature of about 1050C. for a time sufficient to uniformly heat the ingot, slow cooling theingot at a rate of about 30 C. per hour until the ingot is substantiallyat room ternperature, removing surface imperfections from the ingot, hotworking the ingot into a sheet substantially 0.250 thick at atemperature of about 1050 C. followed by hot working the sheet at atemperature of 950 C. from a. thickness of 0.250 of an inch thick to athickness of substantially 0.125 of an inch, and thereafter cold workingthe sheet to a desired thickness at a temperature of about 575 C.

7. The method of making a high temperature and magnetic sheet alloycontaining essentially 16% aluminum, essentially 2% Mo, essentially 0.3%Ti, and the re mainder iron, which consists of melting the constituentsin a suitable melting apparatus to form a molten alloy,

forming the molten alloy into an ingot, controlling the solidificationrate of the molten alloy to produce an ingot having a fine equiaxed castgrain structure, transferring the ingot from the melting apparatus whilered hot to a heating apparatus and heat treating the ingot at atemperature of about 1050 C. for a time sufilcient to uniformly heat theingot, cooling the ingot slowly to substantially room temperature,removing surface imperfections from the ingot, hot working the ingotabove the recrystallization temperature to a sheet of predeterminedthickness, and thereafter cold working the sheet below therecrystallization temperature to a reduced thickness.

8. The method of making a high temperature and magnetic sheet alloycontaining essentially 16% aluminum, essentially 2% molybdenum,essentially 0.3% vanadium, and the remainder iron, which consists ofmelting the constituents together to form a molten alloy, forming themolten alloy into an ingot, controlling the solidification rate of themolten alloy to produce an ingot having a fine equiaxed cast grainstructure, uniformly heating the ingot while the ingot is still red hotto a temperature of 1050" C., slow cooling the ingot at a rate of about30 C. per hour until the ingot is substantially at room femperature,machine working the ingot free of surface imperfections, hot Workingtheingot above the recrystallization temperature into a sheet substantially0.125" thick, and cold working the sheet below the recrystallizationtemperature to the desired thickness.

9. The method of making a high temperature andmagneticsheetalloycontaining essentially 16% aluminum, essentially 2%.rnolybdenum, essentially 0.3% vanadium, and, the remainder iron whichconsists of melting the. constituents in a suitable melting apparatus toform a'molten alloy, formingthe molten alloy into an ingot, controllingthe solidification rate of the molten alloy to produce an ingot having afine equiaxed cast grain structure, transferring the ingot from themelting apparatus while red hot to a heating apparatus'and heat treatingthe ingot at a temperature of. about-1050 C. for a time sufficient touniformly heat the ingot, slow cooling the ingot at a rateof about 30 C.per hour until the ingot is substantially at room temperature, removingsurface imperfections from the ingot, hot-working the ingot into 3:sheet "substantially 0.250" 'thick' at a temperature ofrecrystallization temperature '75 working the ingot into a sheetsubstantially 0.250'.-'

10 about 1050" C. followed'by hot working the sheet at a temperature of950 an inch thick to a thickness of substantially 0.125 of an inch, andthereafter cold Working the sheet to a desired thickness at atemperature of about 575 C.

10. The method of making a magnetic sheet alloy containing essentially16% aluminum, essentially 2% molybdenum, essentially 0.3% vanadium, andthe remainder iron, which consists of melting the constituents in asuitable melting apparatus to form a molten alloy, forming the moltenalloy into an ingot, controlling the solidification rate of the moltenalloy to produce an ingot having a fine equiaxed cast grain structure,transferring the ingot from the melting apparatus while red hot to a theingot at a temperature of about1050 C. for a time sufficient touniformly heat the ingot, cooling the ingot slowly to substantially roomtemperature, removing surface imperfections above the recrystallizationtemperature to a predetermined thickness, and thereafter cold workingthe.

the molten alloy into an ingot, controlling the solidification rate ofthe molten alloy to produce an ingot having a fine equiaxed cast grainstructure, transferring the ingot fromthe melting apparatus while redhot to a heating apparatus and heat treating, the ingot at a temperatureof about 1050 C. for a time sufficient to uniformly heat the ingot, slowcooling the ingot at a rate of about 30 C. per hour until theingot issubstantially at room temperature, removing surface imperfections fromthe ingot, hot working the ingot into a sheet substantially 0.250" thickat at temperatures of about 1050 C. followed by hot working the sheet ata temperature of 950 C. from a thickness of 0.250 of an inch thick to athickness of substantially 0.125 of an inch, and thereafter cold workingthe sheet to the desired thickness at a temperature of about 575 C.

12. The method of making a high temperature and magnetic sheet alloycontaining essentially 16% aluminum, essentially 1% titanium, and theremainder iron, for solid solution strength at high elevatedtemperatures,

which consists of ,melting the constituents together to' forming themolten alloy into an ingot, controlling the solidification rate of themolten alloy form a molten alloy,

above the recrystallization temperature into a sheet substantially0.125. thick, and cold working the sheet below the recrystallizationtemperature to a desired thickness.

13. The method of making a high temperature and magnetic sheet alloycontaining essentially 16% aluminum, essentially 1% titanium, and theremainder iron for solid solution'streng'th at high elevatedtemperatures, 1

which consists of melting the constituents in a suitable meltingapparatus to form a molten alloy, forming the molten alloy into aningot,controlling the-solidification rateof the molten alloy. to produce aningot having a fine equiaxed cast grain structure, transferring theingot from the melting apparatus While red hot to a heating apparatusand heat treating the ingot at a temperature of about 1050 C. for a timesuflicient to uniformly heat theingot, 'slow cooling the ingot at a rateof about 30 C. per hour until the ingot is substantially at roomtemperature, removing surface imperfections from the ingot, hot

C. from a thickness'of 0.250 of high temperature and heating apparatusand heat treating from the ingot, hot working the ingot thick at atemperature of about -1050 working the sheet at a temperature thicknessof 0.250 of anjnch thickto stantially 0.125 of an inch, and thereaftercold working the sheet to'a desired thickness 'ata temperature ofa'bout575 C. V 4

"142The method of making a hightemperature and magnetic sheet alloycontaining essentially 16% aluminum, essentially 1% for solid solutionstrengthening at high elevated temperatures, which consists ofme'ltingthe constituents in a suitable melting apparatus to form a molten alloy,forming the molten alloy into an ingot, controlling .the solidificationrate of the molten alloy to produce aningot'hav'ing a fine equiaxed castgrain structure, transferring the ingot from the melting apparatuswhile'red hot to a heating apparatus and heat treating the ingot at atemperature of about 1050 C. for a time sutlicient to uniformly heat theingot, cooling the ingot slowly to substantially ro'omtemperature,removing surface imperfections from the ingot, hot working the ingotture to a sheet of predetermined thickness, and thereafter cold workingthe sheet below the recrystallization temperaturetoareduced-thickness..

15. The method of making a ferritic high temperature and magnetic alloycontaining from 10 to 18%. aluminum," up to 5% of a strengtheningelement and the remainder'iro'n, which consists of melting and refiningthe C. followed by hot iron ina magnesium oxide crucible usinga vacuumorcontrolled atmosphere, charging the melt with said element' andaluminum, allowing suflicient time to cause thorough mixing, pouring themelt into a mold and allowing it to solidify underhelium or suitableinert atmosphere at a pressure of 5 mm. into a slab substantially oneinch thick, stripping "the slab from said mold while the slab issubstantially red hot, heat treating the slab at 1050 C. for about twohours, cooling slab to about room temperature at-a rate of substantially30 C. per hour, machine working the slab to remove surfaceimperfections, hot working the. slab into a sheet substantially 0.250thick at a temperature of about I050 C. followed by hot working thesheet at about 950 C. to a thicknessv of 0.125", and thereafter coldworking the sheet to a desired thickness at about 575C. I

'16. The method 'o'fmaking a high temperaturea'lumihum-iron base alloycontaining to 18% aluminum and up to 5% of a strengthening element andthe remainder iron, which consists of melting the constituents togetherto form a' molten alloy, forming the molten alloy into an ingot,controlling the solidification rate of the molten alloy guniformly'heating the ingotto a temperature of 105%)"0, siow 'cooling the ingotat a rate of about 30'- C.

perhour until the ingot is substantially at room temperaj ture, removingsurface imperfectionslfrom the ingot, hot

of predetermined thickness Working the ingot into a sheet atatemperature-of about 950 at a temperature of about 575 'C., coldwor'kingithesheet C. to' a reduced thickness,

immersing the cold worked sheet into a hot agitated 20% solution of-NaOHby weight, washing the sheet in water, immersing the sheet in anagitated HNO solution by volume at room temperature, and thereafterwashing the sheetin clear water to remove all and-theoxidecoa'tingformed during .rolling.

of 950. C. from aj a thickness of sub-v titanium, and the remainder iront to above the recrystallization tempera- '50 a fine equiaxed.grains'tructraces of thejHNO;

17. method'ofmaking high temperature and mag 3 netic aluminumeiron basealloys containing 10 to 18% aluminum, 3.3% {molybdenum and the balanceessentially iron into sheet materiaL-which consists of melting 1the-eonstituentsin a melting apparatus to form an alloy melt, 'formingthe melt into. a slab substantially 1' inch thijckjn a cera mi'c mold,stripping .the mold while the-slab :is, red hot, heat treating the, slabat a temperature of; 1050? C. for about 2 hours, slow cooiing "the slab"to substantially room temperature (at .a C. per hour, removing surfaceimperfection rate of 30 slab from the from, the slab, hot reducing th eslab "at a temperature, of 1050? C into sheet m terial substantially 0.250'ofah9 inch thick, hot reducing the sheet material .to a thicknessof substantially 0.125 of an inch thicka't'a temperature 6595-0 0;, andthereafter coldreducingthe sheet a't al temperature of about 575 C. to adesired thickness...

18. The method of making 'a high temperature, and,

magnetic alloy containing from 10 to 18% aluminum, up to 5% of astrengthening element and 'the remainder,

iron, which consists of melting the constituents togethen thereafter.

said alloy being subjected'to a.

0. followed by coolingfat a a high temperature and. comprises producinga aluminum, up the remaihder treating said casting to a temperaturewithin the single phase solid solution region, rapidly cooling thecasting to a temperature within taining the casting at said last namedtemperature for a the multi-phase region, and mainperiod of timesufiicient to precipitate at least one other phase.

20. The method of making a high temperature and magnetic .multi-phasealloy which comprises producing .a melt consisting essentially of 10 to18% to 5% of a strengthening element, and iron, casting said melt andsolidifying the the remainder aluminum, up

same to ,pro-. duce a fine-equiaxed cast grain structure, hot workingthe casting above the recrystallization temperature'to a. desired shape,solution heat treating said shape to a temperature Within the singlephase multi-phase region,

precipitate at least one other phase.

21. The method of making -a high temperature and meltconsisting'essential'ly of 10 to 18% and solidifying the same to producea fin grain structure, solution heat treating said multi-phase region,and maintaining the, casting at said' cipitate at least'one other phase.

22. The method of claim 21 wherein the strengthening titanium." V 23. Ahigh temperature and magnetic ferritic alloy consisting essentially of10 to 18% elements include 3.3% molybdenum and 0.3%

strengthening element, iron, said alloy being fine grain size withdisordered atomic structure.

24. A high temperature and magnetic ferritic alloy consistingessentially of 1010 18% aluminum, up to 5% molybdenum, and the remainderessentially iron, said i by a recrystallized fine grain alloy beingcharacterized size with disordered atomic structure.

25. A hightempera'ture and magnetic ferritic alloy aluminum, up to 5% rtitanium, and the remainder essentially iron, said alloy beingcharacterized by a recrystallized fine grain size consisting essentiallyof 10 to 18% with disordered atomic structure.

26. The method of making a high temperature and from 10 to 18% aluminum,element, and the remainder essentially iron, which consists of meltingthe constituents ,1

magnetic alloy containing up to 5% of strengthening together in asuitable melting apparatus to form a molten solid solution region,flrapidly cooling the shape to a temperature within the. 1

and maintaining the shape atxsaidfi' last named temperature fora periodof time sufiicient to.

e-equiaxed cast 1 casting to a-f. temperature Within the single phasesolid solution region, 1 rapidly cooling the casting .to a temperaturewithin the f aluminum, up to 5% and the remainder essentiallycharacterized by a recrystallized. V

alloy, forming the molten alloy into an ingot, controlling thesolidification rate of the molten alloy to produce a fine equiaxed castgrain structure, annealing the solidified ingot at a temperature ofabout 1050 C. to eliminate stresses therein, cooling the ingot slowly tosubstantially room temperature 'to prevent occurrence of furtherstresses therein, hot working the ingot above the recrystallizationtemperature to a sheet of predetermined thickness, and thereafter coldworking the sheet below the recrystallization temperature to a desiredthickness.

27. A method for making a high temperature magnetic ferritic castingwhich comprises producing a melt consisting essentially of 10 to 18%aluminum, up to 5% of strengthening element, and the remainderessentially iron, casting said melt and controllably solidifying thesame to produce a fine equiaxed cast grain structure, annealing saidcasting at a temperature of about 1050 C. to eliminate stresses therein,and thereafter slowly cooling the casting while avoiding the occurrenceof further stresses therein.

References Cited in the file of this patent UNITED STATES PATENTS1,915,158 Fahrenwald June 20, 1933 1,972,248 Smith Sept. 4, 19342,230,531 Digby Feb. 4, 1941 2,339,842 Digby Jan. 25, 1944 2,523,917Payson Sept. 26, 1950 2,624,669 Crafts Jan. 6, 1953 FOREIGN PATENTS370,012 Great Britain Apr. 1, 1932 409,355 Great Britain Apr. 30, 1954OTHER REFERENCES Metal Progress, vol. 35, No. 6 (1939), G. I. Comstock,page 576.

1. THE METHOD OF MAKING A HIGH TEMPERATURE AND MAGNETIC ALLOY CONTAININGFROM 10 TO 18% ALUMINUM, UP TO 5% OF A STRENGTHENING ELEMENT AND THEREMAINDER IRON, WHICH CONSISTS OF MELTING THE CONSTITUENTS IN A SUITABLEMELTING APPARATUS TO FORM A MOLTEN ALLOY, FORMING THE MOLTEN ALLOY INTOAN INGOT, CONTROLLING THE SOLIDIFICATION RATE OF THE MOLTEN ALLOY TOPRODUCE AN INGOT HAVING A FINE EQUIAXED CAST GRAIN STRUCTURE,TRANSFERRING THE INGOT FROM THE MELTING APPARATUS WHILE RED HOT TO AHEATING APPARATUS AND HEAT TREATING THE INGOT AT A TEMPERATURE OF ABOUT1050*C. FOR A TIME SUFFICIENT TO UNIFORMLY HEAT THE INGOT, SLOW COOLINGTHE INGOT AT A RATE OF ABOUT 30* C. PER HOUR UNTIL THE INGOT ISSUBSTANTIALLY AT ROOM TEMPERATURE, REMOVING SURFACE IMPERFECTIONS FROMTHE INGOT, HOT WORKING THE INGOT INTO A SHEET SUBSTANTIALLY 0.250 OF ANINCH THICK AT A TEMPERATURE OF ABOUT 1050* C. FOLLOWED BY HOT WORKINGTHE SHEET AT A TEMPERATURE OF 950*C. FROM A THICKNESS OF 0.250 OF ANINCH THICK TO A THICKNESS OF SUBSTANTIALLY 0.125 OF AN INCH, ANDTHEREAFTER COLD WORKING THE SHEET OF A PREDETERMINED THICKNESS AT ATEMPERTURE OF 575*C.